Stanford University is the assignee of U.S. Pat. Nos. 5,683,438; 6,602,277; 6,673,099; 6,656,208; 6,966,922; 7,122,047; and 6,974,442. These patents disclose a negative pressure, thermal energy device that can be applied to a patient. The negative pressure device has the following elements: (1) a hard, non-shape altering enclosure having an opening to receive a portion of a patient's body that contains a venous plexus area, (2) a vacuum system that creates a negative pressure in the enclosure, (3) a seal positioned at the enclosure's opening to maintain the negative pressure in the enclosure, and (4) a thermal energy system having a thermal energy contacting element wherein the venous plexus area is exposed to the thermal energy from the thermal energy contacting element.
Enclosure
The enclosure surrounds a portion of a patient's body. In a preferred embodiment, the portion of the patient's body has a venous plexus area. The venous plexus area is a vascular network formed by numerous anastomoses between arteries and veins. A venous plexus area is, along with other locations, normally located at the patient's foot area and/or hand area.
The enclosure can be shaped like a glove, a mitten, a boot, a clam-shell, or equivalents thereof so long as there is an opening that receives the patient's body part. In many embodiments, the enclosure is a polymeric material that can withstand the formation of predetermined negative pressure values within its interior that receives the patient's body part.
Seal
The seal is mounted at the enclosure's opening that receives the patient's body part having a venous plexus area. The seal establishes (1) a vacuum-tight fit between the body portion and the enclosure or (2) a soft seal fit between the body portion and the enclosure.
The term “vacuum-tight”, as interpreted by Dr. Grahn in some of the above-identified Stanford patents and he is one of the inventors of all of the Stanford patents, means a hard seal. In U.S. Pat. No. 7,182,776; Dr. Grahn wrote, “A “hard” seal is characterized as one designed to altogether avoid air leakage past the boundary it provides. In theory, a “hard” seal will allow a single evacuation of the negative pressure chamber for use in the methods. In practice, however, a “hard” seal can produce a tourniquet effect. Also, any inability to maintain a complete seal will be problematic in a system requiring as much.”
A “soft” seal as described herein is characterized as providing an approximate or imperfect seal at a user/seal interface. Such a seal may be more compliant in its interface with a user. Indeed, in response to user movement, such a seal may leak or pass some air at the user/seal interface. In a negative-pressure system designed for use with a soft seal, a regulator or another feedback mechanism/routine will cause a vacuum pump, generator, fan or any such other mechanism capable of drawing a vacuum to respond and evacuate such air as necessary to stabilize the pressure within the chamber, returning it to the desired level. Active control of vacuum pressure in real-time or at predetermined intervals in conjunction with a “soft” seal provides a significant advantage over a “hard” seal system that relies on simply pulling a vacuum with the hopes of maintaining the same.
Some of the Stanford patents disclose the seal is long to “Provide greater seal surface contact with a user.” Greater seal surface contact to the patient increases tissue interface pressure. Increased tissue interface pressure is undesirable.
Vacuum System
The vacuum system connects to the enclosure for generating and, in some embodiments, maintaining a predetermined negative pressure inside the enclosure to cause vasodilation in the body portion surrounded in the enclosure. Negative pressure conditions are a pressure lower than ambient pressure under the particular conditions in which the method is performed. The magnitude of the decrease in pressure from the ambient pressure under the negative pressure conditions is generally at least about 20 mmHg, usually at least about 30 mmHg and more usually at least about 35 mmHg, where the magnitude of the decrease may be as great as 85 mmHg or greater, but typically does not exceed about 60 mmHg and usually does not exceed about 50 mmHg. The negative pressure applied to a portion of the body in the enclosure (a) decreases the temperature when vasoconstriction occurs and/or (b) increases the vasodilation in the body portion that is in the enclosure.
The negative pressure inducing element may be actuated in a number of different ways, including through motor driven aspiration, through a system of valves and pumps which are moved through movement of the mammal in a manner sufficient to create negative pressure in the sealed environment, etc.
Thermal Energy Contacting Element
The thermal energy contacting element transfers thermal energy to, or extracts thermal energy from the body portion in the vacuum enclosure. Whether the thermal energy transfers to or extracts from the body portion depends on the relative temperatures of the thermal energy contacting element and the body portion. The vasodilation in the body portion enhances the exchange of thermal energy between a patient's body core, surface of the body portion, and the thermal energy contacting element.
The thermal energy contacting element has been previously disclosed as (a) a conventional thermal warming plate or blanket, or a conventional thermal cooling plate or blanket, (b) a warm or cool water immersion element, (c) a warming or cooling gas element, and (d) a curved metal plate or a metal tube positioned in the interior of the enclosure.
The three latter embodiments deal with a fluid. In the conduit embodiments, the fluid (i) circulates within it and (ii) does not contact the body portion in the desired area—the venous plexus area. The fluid can be provided by a hypo/hyper/normothermia fluid temperature control device. An example of such a device, and not limited to, is Gaymar's Medi-Therm II hypo/hyper/normothermia fluid temperature control device. That device is disclosed and incorporated by reference in commonly assigned U.S. Pat. No. 6,517,510.
There are problems with the thermal energy contacting surfaces, a patient could elect (a) not to grip the thermal energy contacting element, (b) to re-position the body part, so the body part is not affected by the thermal energy contacting element or (c) to loosen (for example blanket embodiments) the thermal energy contacting element so it does not effectively contact the body part. The patient's election may be unintentional especially if the patient is sedated or under general anesthesia. It is therefore at least one object of the present invention to solve this potential contact problem by making the device invariant to a patient's desire to “grip” or contact the thermal energy contacting element.
Of these thermal energy contacting element embodiments, the metal plate and tube are considered by many to be an effective thermal energy contacting elements because (a) those components are easy to manufacture, (b) the thermal energy transfer efficiency to the patient is relatively acceptable and (c) using the product in actual use is easy.